Question

Question 24 (1 point) ✓ Saved Which of the following includes protostomes and deuterostomes? the coelomates the acoelomates the blastoocoelomates the parazoans Question 25 (1 point) Saved Which of the following organisms is classified as a blastocoelomate (=pseudocoelomate): tapeworm nematode octopus earthworm

Answer 1

1. The Coelomates -

In Protostomes, the coelom forms by a process known as schizocoely. The archenteron initially forms, and the mesodarm splits into two layers: the first attaches to the body wall or ectoderms, forming the parietal layer and the second surrounds the endoderm or alimentary canal forming the visceral layer path. The space between the parietal layer and visceral layer is known as the coelom or body cavity.

In Deuterostomes, the coelomates forms by enterocoely. The archenteron wall produce buds of mesoderm, and these mesodermal diverticula hollow to become the coelomic cavities. Deuterostomes are therefore known as enterocoelomates. Examples of deuterostome coelomates belong to three major clades: chordates (vertebrate, tunicate, and lancelet), echinoderms (starfish, sea urchins, sea cucumbers), and hemichordates (acorn worms and graptolites) .

2. The Nematodes

Pseudocoelomate animals have a pseudocoelom (literally "false cavity"), which is a fluid filled body cavity. Tissue derived from mesoderm partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate. All pseudocoelomates are protostomes; however, not all protostomes are pseudocoelomates. An example of a Pseudocoelomate is the roundworm. Pseudocoelomate animals are also referred to as Blastocoelomate.

Acoelomate animal, like flatworms, have no body cavity at all. Semi-solid mesodermal tissues between the gut and body wall hold their organs in place.